Linseed is the most common oil effectively used to enhance the drying time in paints. Linseed oils are sustainable, last longer and non-toxic with a good environmental profile. Linseed oils are widely used in applications such as concrete, decks, and protection of wood taking advantage of the linseed oil's unique drying properties via slow oxidation on exposure to oxygen and UV light. The drying properties are very similar to solvent based paint and have always been explored to obtain solvent free paint. Drying time is about the same for linseed oil paint as solvent-based based oil paint; however, as linseed oil dries by exposure to oxygen and UV-light, different weather conditions can slightly change the drying times.
Linseed oil is used in solvent and water based paints. In solvent based paints, traditionally straight linseed oil with mineral spirits is used, whereas in the water based pains, the linseed oil in used as an emulsion for easy incorporation. As the linseed oil starts polymerizing in the drying process, the linseed oil protects the water evaporation and leaves a hard film on the surface. This concept has been used for years. However, the linseed oil emulsion is usually available as 50:50 oil/water systems. Such emulsions are not kinetically stable and tend to separate with the environmental condition that limits the shelf life on storage and transportation.
In the paint and coating industries, a universal colorant is one that is designed for use in water borne and solvent borne systems. When universal colorants are added to water borne systems, many changes in the physical properties are encountered in the tint base. The most common effect is the viscosity changes associated with the addition of the colorant, as well as the effect on color development. The main reasons for effects seen with poor color development is due to the improper color compatibility between the colorant and the tint base which results in pigment separation and/or flocculation during the drying of the resultant film. However, typical dispersants used in universal colorants are not biobased and finding a biobased dispersant that is compatible with a universal colorant is a challenge.
In addition to uses in paint, linseed oil is used in concrete applications for a number of benefits. Emulsions of boiled linseed oil have certain physical characteristics suitable for application in concrete as curing and antispalling agents. Curing of wet concrete with the use of a spray technique is believed to retard concrete deterioration and reduce spoiling when the concrete is subjected to winter deicing salts. Emulsions of linseed oil are effective in protecting air entrained concrete from damage that results from the application of deicing materials and concurrent freeze-thaw cycles. The linseed oil emulsions are effective as curing and antispalling agents in concrete.
Other oil emulsions have various uses. For example, methylated seed oil emulsions have many applications such as in oil fields, cleaning, and in the agricultural adjuvant industry. Further, limonene is quite commonly used in cleaning and degreasing applications. If without fine tuning one can make customize product and application by just changing the oil type a great advantages are seen as far as cost savings and transportation are concerned.
However, each of the oil emulsions has drawbacks. For instance, such emulsions are typically made using high energy mixing. The particle is size of the oil droplet in the emulsion is the key towards producing a stable emulsion. Oil and water homogenized at high shear usually results in fine droplet sizes that have a higher surface area and interact better with the added surfactant in stabilizing the emulsion. Keeping such oil and water emulsions stable over time can be a challenge.
Microemulsions are self-assembled systems, form spontaneously with no high energy mixing, and have excellent stability. Further, if a given microemulsion surfactant concentrate can solubilize different types of oils, such microemulsion offers tremendous opportunity towards applications based on the specific oil needs. Thus, needs exist for microemulsions which are able to solubilize such oils.